JP2007159297A - High-frequency heating inverter apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-frequency heating inverter apparatus having a simple constitution, electrically balancing currents flowing in the switching elements, and surely preventing the switching elements from damages. <P>SOLUTION: The high-frequency heating inverter apparatus comprises a plurality of arms, bridge-connected and having the semiconductor switching elements, and current-balancing means connected between a common terminal and each switching means. The current-balancing means are each provided with a core having a plurality of through holes that form at least four openings and a pair of conductors inserted from one opening of each through hole of the core toward the other opening and connected in series between each through hole. A pair of the conductors is configured to set a current in the reverse direction in each through hole of the core. The core is formed by joining an E-type core and an I-type core or a pair of the E-type cores. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inverter device for high frequency heating that can be suitably used, for example, as a high frequency induction heating device.

  Conventionally, as an inverter device used when brazing a cemented carbide chip to a circular saw base metal using high-frequency induction heating, for example, as disclosed in Patent Document 1, four switching elements are used. It is known that a full bridge is connected, a diode is connected in series to each of the switching elements, and a resistor is connected in parallel to the diode.

  However, in this inverter device, if there are variations in the electrical characteristic values of the diodes or switching elements connected in series to the switching elements, the current flowing through the switching elements connected in parallel becomes unbalanced, and A large current concentrates on the switching element, and the switching element may be damaged.

Therefore, in order to eliminate such inconvenience, the present applicant applied for an inverter device shown in Patent Document 2. This inverter device includes a pair of switching elements connected in parallel and a rectifying element connected in series to each of the switching elements, and connects the switching element and the rectifying element with a thin copper plate. The current flowing through each switching element is balanced by the number of sheets.
Japanese Utility Model Publication No. 1-162779 JP 2000-278957 A

  However, in such an inverter device, although the current flowing through each switching element can be balanced to some extent by adjusting the number of copper plates, particularly with an inverter device requiring a high current at a high frequency or a detachable heating coil. Inverter devices and the like that are difficult to match, it is difficult to effectively and reliably balance the currents flowing through the switching elements, and the switching elements are still easily damaged.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a high-frequency circuit that can electrically prevent the current flowing through each switching element with a simple configuration and reliably prevent damage to each switching element. The object is to provide an inverter device for heating.

  In order to achieve this object, the invention according to claim 1 of the present invention is configured by bridge-connecting a plurality of arms having semiconductor switching elements, and a current is connected between the common terminal and each semiconductor switching element. An inverter device for high-frequency heating provided with balancing means, wherein the current balancing means includes a core having a plurality of through holes forming at least four openings, and from one opening of each through hole of the core to the other. And a pair of conductors connected in series between the through-holes, and the pair of conductors has a current set in the opposite direction in each through-hole portion of the core. It is characterized by.

  The invention according to claim 2 is characterized in that the core has two through-holes by joining an E-type core and an I-type core or a pair of E-type cores. The invention described in 1 is characterized in that the pair of conductors are formed by laminating a plurality of thin copper plates, and are disposed to face each other in a predetermined direction in the through hole of the core.

  According to the first aspect of the present invention, a pair of conductors are provided in each of the plurality of through holes provided in the core between the common terminal of each arm connected in a bridge connection and the semiconductor switching element of each arm. Current balance means inserted in series so that the current direction is reversed, a plurality of series balance parts are formed in the current balance means, and the current flowing through each arm in parallel connection is Each semiconductor switching element can be effectively balanced by each balance part of the current balance means, and can electrically and efficiently eliminate the current imbalance that is likely to occur when there is a large current or heating coil matching failure. Can be reliably prevented.

  According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the core joins the E-type core and the I-type core or the pair of E-type cores, thereby providing two through holes. Therefore, the core can be easily formed by joining existing cores such as an E-type core and an I-type core, and the configuration of the current balance means can be simplified and inexpensively formed.

  Further, according to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, the pair of conductors are formed by laminating a plurality of thin copper plates, and the inside of the core through-hole is formed. Since the copper plates are arranged opposite to each other in a predetermined direction, the current capacity of the conductor can be sufficiently secured by the high-frequency current flowing through the surface layer of each copper plate by laminating the thin copper plates, and the use of the thin plate facilitates the bending of the copper plate, for example. The conductor can be easily manufactured.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 to 3 show an embodiment of an inverter device for high-frequency heating according to the present invention, FIG. 1 is a basic circuit diagram thereof, FIG. 2 is a circuit diagram of current balance means, and FIG. 3 is a specific structure thereof. It is the side view made into the front view and the partial cross section.

  In FIG. 1, the inverter apparatus 1 has eight IGBTs 3a to 3h as semiconductor switching elements connected to eight arms 2a to 2h, respectively. In each arm 2a to 2h, 2a and 2b, 2c and 2d, 2e and 2f, 2g and 2h are connected in series, and one end of the arms 2a, 2c, 2e and 2g is connected to the common terminal 4a on the positive side of the DC power supply. The other ends of the arms 2b, 2d, 2f, and 2h are connected to the negative common terminal 4b of the DC power supply, thereby forming the full bridge circuit 1a.

  One output terminal 5a is connected to the connection point between the arms 2a and 2b and the arms 2c and 2d, and the other output terminal 5b is connected to the connection point between the arms 2e and 2f and the arms 2g and 2h. A primary coil of the transformer 6 is connected to the pair of output terminals 5a and 5b, and a load 7 such as a CT or a heating coil is connected to the secondary coil of the transformer 6. Current balancing means 8 is provided between the common terminal 4a and the drains of the IGBTs 3a and 3c and between the drains of the IGBTs 3e and 3g, respectively, and between the common terminal 4b and the sources of the IGBTs 3b and 3d and IGBTs 3f and 3h. The current balance means 8 is also provided between the sources.

  As shown in FIG. 2, the current balance means 8 includes a core 10 having two through holes 11 and 12, and a pair of conductors 13 and 14 inserted in series in the through holes 11 and 12 of the core 10. It is formed by what is called a differential transformer. The core 10 has four openings 11a, 11b, 12a, 12b formed at both ends of two through holes 11, 12 formed as described later, and a pair of conductors is formed in each of the through holes 11, 12. 13 and 14 are inserted as follows.

  That is, the conductor 13 is inserted from one opening 11a of one through-hole 11 toward the other opening 11b and bent downward, and further from the other opening 12b of the other through-hole 12 toward one opening 12a. For example, the end portion is drawn downward. Further, the conductor 14 is inserted from the other opening 11b of one through hole 11 toward the one opening 11a and bent downward, and further, from one opening 12a of the other through hole 12 to the other opening 12b. For example, the end portion is drawn downward. And the drawer | drawing-out part of each conductor 13 and 14 below is connected to the predetermined | prescribed terminal of predetermined | prescribed IGBT3a-3h via the copper plate etc. which are not shown in figure. Thereby, the conductor 13 and the conductor 14 drawn out from the common terminals 4a and 4b are inserted in the through holes 11 and 12 of the core 10 in the reverse direction, and the balance portions 8a and 8b are formed in the through holes 11 and 12, respectively. Has been.

  FIG. 3 is a front view and a side view showing a specific configuration of the current balance means 8. As shown in the drawing, the core 10 of the current balance means 8 is integrated by fixing the opening end of the E-type core 10a and the I-type core 10b with an adhesive, and the two through holes 11, 12 are integrated. It is formed to have The conductor 13 and the conductor 14 inserted in series in the openings 11a, 11b, 12a, and 12b of the core 10 have one lead-out portion 13a and 14a, the other lead-out portion 13b and 14b, and a pair of core insertion portions. 13c, 14c and the core insertion parts 13c, 14c are connected to each other by connecting the parts 13d, 14d at predetermined positions (for example, between the connection parts 13d, 14d and one core insertion part 13c, 14c). It is formed in a substantially symmetrical shape.

  The flat conductors 13 and 14 having a predetermined width are arranged in a direction substantially orthogonal to the thickness direction of the core 10, and the conductors 13 and 14 are displaced in the width direction of the through holes 11 and 12. The core insertion portions 13c and 14c of the conductors 13 and 14 are arranged to face each other in a planar shape in the through holes 11 and 12, so that the two balance portions 8a and 8b are formed. At this time, the arrangement positional relationship between the core insertion portions 13c and 14c of the conductor 13 and the conductor 14 in each of the through holes 11 and 12 is not limited to the planar shape in the width direction, but is shown by a two-dot chain line in FIG. In addition, the conductor 13 may be arranged obliquely above and below the through holes 11 and 12 and the conductor 14 may be arranged obliquely below the through holes 11 and 12. The conductor 13 and the conductor 14 have a plate thickness of about 0.3 to 1 mm and a width of about 10 to 20 mm as shown in an enlarged view in FIG. It is formed by laminating a plurality (four in the figure) of thin copper plates 15 that have been subjected to an insulation treatment 17 by coating, winding of insulating tape, or the like.

  A drive circuit (not shown) composed of a predetermined oscillation circuit (external excitation or self-excitation) or the like is connected to the gates of the IGBTs 3a to 3h shown in FIG. 1, and the IGBTs 3a to 3h are driven by a drive signal (bias) of the drive circuit. Is turned on / off, and a predetermined high-frequency current is obtained between the output terminals 5a and 5b. Further, for example, a transformer type current detector (not shown) is connected to the source side of each of the arms 2b, 2d, 2f, and 2h, and this is detected when an abnormal current flows through each arm 2a to 2h. The drive circuit is immediately stopped to stop the on / off operation of the IGBTs 3a to 3h (cut off the current supply). An electrolytic capacitor 21 for supplying a predetermined charge (electric power) to the arms 2a to 2h is connected between the common terminals 4a and 4b of the inverter device 1, and an electrolytic capacitor is provided when the inverter device 1 is abnormal. A series circuit of a resistor 22 for discharging the electric charge 21 and a diode 23 is connected.

  Next, the operation of the inverter device 1 using the current balance means 8 will be described. When a predetermined drive signal is applied between the gates and sources of the IGBTs 3a and 3c and the IGBTs 3f and 3h from the drive circuit, the IGBTs 3a, 3c, 3f and 3h are turned on, and a common DC power source is used. From the terminal 4a, a current flows through the arms 2a and 2c as shown by an arrow A, and this flows to the common terminal 4b through the primary coil of the transformer 6 and the arms 2f and 2h.

  Further, when the IGBTs 3b, 3d, 3e, and 3g are turned on by the drive signal, current flows from the common terminal 4a through the arms 2e and 2g as indicated by the arrow b, and this flows through the primary coil of the transformer 6, the arms 2b and 2d. The current flows in the opposite direction to the arrow A. Then, by alternately turning on and off the IGBTs 3a, 3c, 3f, and 3h and the IGBTs 3b, 3d, 3e, and 3g, a reverse current flows alternately on the primary side of the transformer 6, and the secondary of the transformer 6 A high-frequency sine waveform is output to the side, this high-frequency current is converted into a large current by CT or the like and supplied to the heating coil, and the work is induction-heated, for example, by the magnetic flux generated from the heating coil.

  At this time, the currents flowing through the arms 2 a to 2 h of the inverter device 1 are balanced by the current balance means 8 so as to be substantially the same current. That is, the current balance means 8 comprising a differential transformer is connected in series between the plus common terminal 4a and minus common terminal 4b of the DC power source and the IGBTs 3a to 3h of the arms 2a to 2h. For example, when the magnitudes of the current values flowing through the conductors 13 and 14 of the arms 2a and 2c are different, the current balance means 8 serves as a resistor for suppressing an increase in current for the conductors 13 and 14 through which a large current value flows. The current balance means 8 generates an electromotive force that increases the current for the conductors 13 and 14 through which a small current flows.

  Since the current balance means 8 has the two balance portions 8a and 8b on the upstream side and the downstream side, the unbalanced current or the like that could not be sufficiently balanced by the balance portion 8a on the upstream side becomes the balance portion 8b on the downstream side. Therefore, the current unbalance is surely eliminated. Since the current balance means 8 is connected to the common terminal 4a and the common terminal 4b, the current balance means 8 allows the arms 2a and 2c, arms 2b and 2d, arms 2e and 2g, and arms 2f and 2h to be connected. The flowing currents are balanced. At this time, since a plurality of copper plates 15 laminated as the conductors 13 and 14 are used, a high-frequency current flows through the surface layer of each copper plate 15, and the conductors 13 and 14 having a predetermined current capacity can be easily obtained. The current values flowing through the arms 2a to 2h (the IGBTs 3a to 3h) of the full-bridge inverter device 1 are balanced to be substantially the same. Balance is effectively eliminated.

  As described above, according to the inverter device 1 of the above embodiment, among the arms 2a to 2h connected to the full bridge, a pair of arms 2a to 2h in parallel (for example, the arms 2a and 2c or the arms 2e and 2g). Current balance means 8 is provided between each of the IGBTs 3a to 3h and the positive common terminal 4a and the negative common terminal 4b of the DC power supply, so that the current flowing through the pair of arms 2a to 2h can be balanced. Thus, it is possible to prevent damage such as burning of the IGBTs 3a to 3h due to current imbalance (overcurrent).

  In particular, the current balance means 8 includes two through-holes 11 and 12 and a pair of conductors 13 and 14 inserted through the through-holes 11 and 12 in opposite directions, so that two balance portions 8a on the upstream side and the downstream side are provided. 8b, the unbalanced current that could not be balanced by the upstream balance unit 8a can be balanced by the downstream balance unit 8b, resulting in a high-frequency high power inverter device 1 and the like. Easy current imbalance can be balanced with extremely high accuracy.

  The conductors 13 and 14 are formed of a copper plate 15 having a predetermined width, and the lead portions 13a, 13b, 14a and 14b, the core insertion portions 13c and 14c, and the connecting portions 13d and 14d are formed by bending a predetermined position of the copper plate 15. Since these are formed by connecting them at predetermined positions by soldering or brazing, it is easy to manufacture the substantially symmetrical conductors 13 and 14 using the copper plates 15 having substantially the same shape. It can be carried out. In particular, since the conductor 13 and the conductor 14 are formed of a plurality of laminated thin copper plates 15 and a predetermined surface thereof is insulated, for example, the copper plate 15 can be easily bent, and each of the conductors 13, 14. Can be manufactured more easily and inexpensively.

  Further, since the core 10 through which the core insertion portions 13c and 14c of the conductors 13 and 14 are inserted is formed by joining the E-type core 10a and the I-type core 10b, the existing cores 10a and 10b are used. The core 10 having two through holes 11 and 12 can be formed, and the cost of the core 10 itself can be reduced, and the cores of the conductors 13 and 14 are inserted through the opening of the E-type core 10a. By inserting the I-type core 10b after inserting the portions 13c and 14c, the conductors 13 and 14 and the core 10 in the divided state can be easily inserted into the through holes 11 and 12 of the core 10 of the conductors 13 and 14, respectively. Can be done.

  Furthermore, since a plurality of thin copper plates 15 are used as the conductors 13 and 14, the current capacity of the conductors 13 and 14 is sufficiently secured by the high-frequency current flowing through the surface layer (surface) of each copper plate 15. Therefore, it is possible to accurately cope with a high-frequency current of a large current. As a result, the manufacturing cost of the conductors 13 and 14 can be reduced, the assembly cost and the maintenance cost can be reduced, and the parts cost can be reduced by preventing damage to the IGBTs 3a to 3h. Even if the power type inverter device 1 or the heating coil is detachable and the type of the inverter device 1 is likely to cause a matching failure with the heating coil, it is possible to easily provide a high-performance device that is inexpensive and has few failures. It becomes.

  Further, for example, if a winding (not shown) is wound around the core 10 and a current induced in the winding is detected so that the current balance means 8 also has an abnormality detection function, the DC power supply common terminal 4a, Abnormal current can be quickly detected by the current balance means 8 provided on the 4b side, damage to the IGBTs 3a to 3h can be more reliably prevented, and the current balance means 8 can also be used as an abnormal current detection function. An abnormality detection device can be obtained.

  FIG. 4 is a front view and a side view similar to FIG. 3 showing a modification of the current balance means 8. Hereinafter, the same parts as those in the above embodiment will be described with the same reference numerals. The characteristic of the current balance means 8 in this example is that the flat conductor 13 and the conductor 14 are arranged so as to be substantially parallel to the thickness direction of the core 10. That is, the core insertion portions 13c and 14c of the conductors 13 and 14 are opposed to each other with a predetermined gap in a planar shape within the through holes 11 and 12 of the core 10, and the balance portion is provided by the opposed arrangement portions. Portions 8a and 8b are formed. In this modified example, in addition to the same effects as those of the above embodiment, the core insertion portions 13c and 14c of the conductors 13 and 14 can be arranged close to each other to increase the coupling coefficient of the differential transformer, thereby improving the balance efficiency. It is possible to achieve effects such as further improving

  In addition, in the said embodiment, although the case where the inverter apparatus 1 was one full bridge circuit 1a which has eight arms 2a-2h was demonstrated, this invention is not limited to this, For example, a half bridge inverter apparatus It can also be applied to the inverter device 1 in which a plurality of bridge circuits 1a and 1a, 1b,... When a plurality of sets of the full bridge circuits 1a and 1b are arranged in parallel, the current balance means 8 may be provided in each arm of the full bridge circuits 1a and 1b. In this case, the full bridge circuits 1a and 1b It is also possible to provide a predetermined number of current balance means on the input side as an input synthesis circuit, or to provide a predetermined number of current balance means 8 on the output side of each full bridge circuit 1a, 1b as an output synthesis circuit.

  Moreover, in the said embodiment, although the case where the number of the through-holes 11 and 12 provided in the core 10 is two, ie, the number of the balance parts 8a and 8b of the electric current balance means 8, is two, for example in the core 10 is demonstrated. It is good also as a structure which provides 3 or more through-holes (3 or more balance parts in the current balance means 8), and when providing 3 or more through-holes in the core 10, each through-hole is arrange | positioned linearly or a circumference | surroundings Appropriate arrangement forms such as arranging them in a shape can be adopted. Furthermore, the conductors 13 and 14 in the present invention are not limited to the laminated copper plates 15, but may be a single copper plate or a conductor such as an electric wire.

  Moreover, in the said embodiment, although the shape (opening shape) of the through-holes 1 and 12 of the core 10 was formed in square shape, for example, as shown by the dashed-two dotted line of FIG. The core 10 itself is not limited to the integration by joining the E-type core 10a and the I-type core 10b. For example, as shown in FIG. It can also be formed by bonding.

  Furthermore, in the above-described embodiment, the IGBTs 3a to 3h are used as semiconductor switching elements, but various semiconductors having a switching function such as normal transistors, thyristors, and FETs can be used. Moreover, the circuit example of the inverter apparatus 1 in the said embodiment, the form of the copper plate 15 (conductors 13 and 14), etc. are examples, for example, diode, resistance, a capacitor, a coil, etc. are added to IGBT3a-3h of each arm 2a-2h. The circuit configuration can be changed as appropriate without departing from the gist of the present invention, such as a circuit configuration that prevents damage to the IGBTs 3a to 3h by connecting them in series or in parallel.

  In addition to inverter devices for high-frequency induction heating devices such as brazing, quenching, and annealing, the present invention is used for various electromagnetic cookers such as microwave ovens and induction heating (IH) cookers, and for driving motors, electric motors, fluorescent lamps, etc. The present invention can also be applied to various inverter devices for circuits.

1 is a basic circuit diagram showing an embodiment of an inverter device according to the present invention. The circuit diagram of the current balance means Front view and partial cross-sectional side view of the current balance means Front view and side view similar to FIG. 3 showing a modification of the current balance means

Explanation of symbols

  1: inverter device, 1a, 1b: full bridge circuit, 2a-2h: arm, 3a-3h: IGBT, 4a, 4b: common terminal, 5a, 5b: output terminal, 6: transformer, 7: load, 8: current Balance means, 8a, 8b: balance part, 10: core, 10a: E type core, 10b: I type core, 11, 12: through hole, 11a, 11b, 12a, 12b: opening, 13, 14: conductor, 13a , 13b, 14a, 14b: drawer portion, 13c, 14c: core insertion portion, 13d, 14d: connecting portion, 15: copper plate.

Claims (3)

A high-frequency heating inverter device comprising a plurality of arms having semiconductor switching elements connected by bridges, and provided with current balancing means between the common terminal and each semiconductor switching element,
The current balancing means includes a core having a plurality of through holes forming at least four openings, and is inserted from one opening of each through hole of the core toward the other opening, and in series between the through holes. And a pair of conductors connected in a state, wherein the pair of conductors has a current set in the opposite direction in each through-hole portion of the core.   2. The high frequency heating inverter device according to claim 1, wherein the core has two through holes by joining an E type core and an I type core or a pair of E type cores.   3. The high-frequency heating device according to claim 1, wherein the pair of conductors are formed by laminating a plurality of thin copper plates, and are disposed to face each other in a predetermined direction in the through hole of the core. Inverter device.

Images